docs: def get_credentials(env=None):
      """
      Gets the TextMagic credentials from current environment
  
      :param env: environment
      :return: username, token
      """
      environ = env or os.environ
      try:
          username = environ["TEXTMAGIC_USERNAME"]
          token = environ["TEXTMAGIC_AUTH_TOKEN"]
          return username, token
      except KeyError:
          return None, None